Such a steering device is known from DE 19813474 A1. The vehicle wheels are activated via a hydraulic steering system, the steering wheel rotation being detected via a hydraulic steering valve on the carriage, which is connected via flexible hydraulic lines to the fixed part of the steering system. In order that the hydraulic lines can be carried along upon displacement of the carriage, they must be situated in a loop, for which relatively complex, covered line guides must be provided in order to protect them against damage. The lines are subject to undesired mechanical strain during a movement of the carriage. In addition, the line guiding restricts the free surface area available in the cab for the driver.